1. Field
The present invention relates generally to methods and apparatus for manufacturing ceramic materials and, more particularly to methods and apparatus for heating and drying ceramic green bodies with microwaves.
2. Technical Background
Conventional heating or drying comprising convectional or a combination of convectional and radiative gas or electric resistance heating is commonly used in the manufacture of ceramic materials to remove moisture from ceramic green bodies. However, the heating rate, temperature control and application of heat associated with these conventional heating methods often results in high energy consumption and inconsistent product quality.
Industrial heating by microwave radiation has been used to accelerate the drying of ceramic green bodies. In comparison with conventional heating, microwave heating provides a higher heating rate and is generally faster than conventional drying because the ceramic body is heated directly through the interaction of the microwave energy with the ceramic green body. A single microwave applicator or a plurality of microwave applicators may be employed to heat and dry the ceramic green bodies.
However, while heating and drying ceramic green bodies by the application of microwave energy offers advantages over other heating and drying methods, microwave heating and drying systems currently used also have several drawbacks. For example, current microwave heating and drying systems do not adequately account for load variations in the microwave heating chamber of the heating and drying system which may result in temperature variations between individual ceramic green bodies dried under the same conditions. The temperature variations between individual ceramic green bodies may decrease the throughput of the microwave heating and drying system as some ceramic green bodies may not be adequately dried and, as a result, may need to be reprocessed. Alternatively, the ceramic green bodies may be over dried which can result in cracking. Moreover, the quality and consistency of the resultant ceramic material may be adversely affected due to variations in the moisture content of the ceramic green bodies following drying.
Accordingly, a need exists for alternative methods, apparatus and systems for heating and drying ceramic green bodies with microwave energy.